In retrospect, Paula Hawkins realizes that sending her half-finished thriller to publishers before she'd written the crucial, explosive final scenes might seem like a brazen act of overconfidence. At the time, though, she badly needed the money.

"I was kind of broke," Hawkins said over coffee recently in the drafty, pigeon-infested food court in Paddington Station here, pausing occasionally when she was drowned out by announcements from the station agent. "The Girl on the Train was a last roll of the dice for me as a fiction writer."

As gambles go, this one has more than paid off for Hawkins and her publisher. In less than a month, The Girl on the Train, a slow-building suspense novel that hinges on a young woman's disappearance and features three shifty female narrators, has catapulted to the top of the best-seller lists. Next week it will hold the Number one spot on the hardcover and e-book fiction lists of The New York Times.

Hawkins seems slightly stunned by the sudden attention, particularly the book’s resonance with readers in the United States. Her American publisher, Riverhead, has reprinted the novel 10 times and now has nearly 500,000 copies in print, up from a planned first printing of 40,000.

The idea for the story struck Hawkins years ago on her morning commute, when she often found herself staring into the yards and windows of homes she passed. She wondered what she would do if she saw something sinister. "What, if on some train journey or other, you see something?" she asked. "How would you later stand as a witness?" As an unknown author, Hawkins wasn't pegged to be an instant international sensation. American crime fiction travels easily abroad; the converse is less often true, unless the author happens to be a J K Rowling or a Lee Child. But The Girl on the Train may have benefited from a wave of popular and unconventional suspense novels that have eroded the already thin boundary between literary fiction and thrillers.

Hawkins joins the ranks of a new generation of female suspense novelists – writers like Megan Abbott, Tana French, Harriet Lane and Gillian Flynn – who are redefining contemporary crime fiction with character-driven narratives that defy genre conventions. Their novels dig into social issues, feature complex women who aren’t purely victims or vixens, and create suspense with subtle psychological developments and shifts in relationships instead of procedural plot points and car chases.

Sarah McGrath, who acquired The Girl on the Train as editor-in-chief of Riverhead, said she normally doesn't read or buy thrillers but made an exception for Hawkins' novel. "We do more boutique literary publishing, but this book is so perfectly crafted that it belonged on our list," she said.

Hawkins, 42, seems equally wary of being pigeon-holed as a crime writer. When her stroll through London’s upscale Marylebone neighborhood during an interview brought an accidental detour onto Baker Street, the home of England’s most famous fictional detective, she seemed mortified. “Sorry, this wasn’t planned,” she said, walking briskly past a line of tourists at the Sherlock Holmes Museum.

All the fuss began with what was a desperate and somewhat mercenary move by Hawkins to reinvent herself as a suspense writer. Born and raised in Harare, Zimbabwe, Hawkins grew up in thrall to foreign correspondents who tracked in and out of her house to visit her father, an economics professor and financial journalist. She moved to London with her family when she was 17. When her parents returned to Zimbabwe a few years later, she stayed in England to attend Oxford, studying economics, politics and philosophy, and eventually became a business reporter for The Times. She wrote The Money Goddess, a financial advice book for women that she seems slightly embarrassed by now. ("I wouldn't urge anyone to go out and by it," she said apologetically.)

About six years ago, she pivoted to fiction in a somewhat clandestine way. Her literary agent approached her with a proposal to write a romantic comedy about a woman who loses her job in the recession. Hawkins cranked out Confessions of a Reluctant Recessionista in about two months and published it under the pen name Amy Silver. Three more Amy Silver novels followed.

The books didn't sell especially well, and after a while, Hawkins began to tire of frothy romantic tropes. A low point was an assignment from her publisher to write All I Want for Christmas, a holiday-themed romantic comedy. "I'm not romantic, and I don't like Christmas," she said.

Hawkins found herself injecting violence and tragedy into what was meant to be lighthearted fluff. She killed off one character in a bombing in Afghanistan. Another was felled by a drunken driver. “The books kept getting darker and more miserable,” she said. “I realized I do tragedy better than comedy.”

Two years ago, with her finances faltering, she decided to try writing the kind of story she likes to read. She unearthed an old idea for a character who struggles with alcoholism and frequently blacks out, which becomes more than a personal issue when this heroine realises that she may have witnessed a serious crime and can’t recall the specifics.

Hawkins wrote the first half in a feverish four months, and her agent sent it out to publishers to see if anyone would bite. A bidding war erupted. The Girl on the Train unfolds in a bland London suburb where the protagonist, Rachel, finds her life dissolving into a series of gin-fueled benders after she has tried and failed to get pregnant, and her husband leaves her for another woman. Rachel becomes obsessed with a seemingly happy couple she spies on through the window on the train to London each day. When the woman, Megan, disappears, Rachel becomes convinced that she witnessed something that's crucial to solving the mystery. But she can't trust her own memory, much less earn the trust of the police or the woman's distraught husband.

The themes of domestic violence and alcohol and drug abuse, and the slippery question of whether people can ever truly know their spouses or themselves, make the story more complex than the average thriller. “I know people like to read about serial killers and spies, but most of us will never encounter these things,” Hawkins said. “Sadly, most of the threats we encounter are at home.” Hawkins described her own life as “really boring.” She lives in a small Victorian house that she shares with an ex-boyfriend near a men’s prison in south London. She says she prefers England’s leaden skies to her native country’s warmth and sunshine because they justify her impulse to stay in, reading and writing. “I like bad weather – it suits my mood,” she said.

Her life is about to get more action-packed. Riverhead is sending Hawkins on an eight-city North American tour that starts this weekend. DreamWorks has optioned the film rights and has hired Erin Cressida Wilson (who worked on Secretary) to write the screenplay. Foreign rights have been sold in 34 countries.

She has another book under contract, a Gothic-tinged psychological thriller about sisters that she says is now a month overdue. Like The Girl on the Train, it's not a conventional crime story. "There doesn't always need to be a killing in it," Hawkins said. "But there's an atmosphere of menace that infects the everyday."

– The New York Times service